Study On Preparation Of Furfural Derivatives By Monosaccharide Transformation Catalyzed By γ-Al ₂ 3 Nanofibers Supported Catalysts

5-hydroxymethylfurfural(5-HMF) and furfural as important platform chemicals,can be used to synthesize a variety of chemical intermediztes which are widely used in chemical industry, fuel and so on, through a series of reactions such as hydrogenation, hydrolysis, halide and esterification. 5-HMF and furfural mainly comes from the transformation of polysaccharide, oligosaccharides and monosaccharides and sugar widely exist in nature, for example, glucose is the main composition of biomass. Monosaccharides(such as glucose, fructose, xylose and so on) dehydrate to 5-HMF and furfural under the effect of solvent and catalyst. Water is environment friendly, cheap and the best choice as the solvent, but will promote the rehydration reaction of product to levulinic acid, formic acid and other by-products, which affect the yield. So researchers focus on the research of non-aqueous solvent systems, and non-aqueous solvent can inhibit effectively product`s rehydration to improve the yield. Catalyst plays a crucial role in the conversion of monosaccharide to 5-HMF or furfural and consists of homogeneous and heterogeneous catalysts. The homogeneous catalyst is not easy to be separated from reaction mixture, can not be recycled and cause the waste of resources. In comparison,the heterogeneous catalyst is on the contrary and is more popular.It is known that conversion of glucose to 5-HMF is a two-step reaction. The first step is the isomerization of glucose to fructose catalyzed by Lewis acid and the second step is the dehydration of generated fructose from glucose to 5-HMF in Br?nsted acid conditions which is not benefit on the first step. So catalytic activity on the reaction of glucose conversion to 5-HMF depends on the Br?nsted/Lewis acid site ratio in the catalyst and this is a challenge of catalyst on monosaccharide conversion.This study intended to use γ-Al2O3 nanofiber coated with Nb2O5, WO3 and ZrO2 whose Br?nsted/Lewis acid site ratio was changed with loading capacity, to catalyze dehydration reactions of fructose and glucose to 5-HMF and xylose to furfural in DMSO. The catalyst was characterized by XRD, SEM, TEM and BET and the yield of product was calculated by high performance liquid chromatography(HPLC)combined with internal standard method. The yield of 5-HMF from fructose at150 ℃、5 h by Nb2O5-Al2O3, WO3-Al2O3, ZrO2-Al2O3 reached maximums 78.54%,78.74% and 75.53% at loading capacity of 40 wt%,1 wt% and 40 wt%, respectively.In the reaction of glucose to 5-HMF at 150 ℃、4 h, the max yields of 5-HMF were55.93%, 51.93% and 24.86% at loading capacity of 1 wt%,50 wt% and 40 wt%, inorder. At 150 ℃、6 h, furfural yields in the dehydration reaction of xylose separately reached up to 56.07%, 55.90% and 53.42% at loading capacity of 1 wt%,50 wt% and5 wt%. In addition, we prepared supported catalysts(B2O3-Al2O3, V2O5-Al2O3,Fe2O3-Al2O3) and studied their catalytic activities through reaction with fructose,glucose and xylose.